Underfill dispensing with controlled fillet profile

ABSTRACT

A method includes placing an underfill-shaping cover on a package component of a package, with a device die of the package extending into an opening of the underfill-shaping cover. An underfill is dispensed into the opening of the underfill-shaping cover. The underfill fills a gap between the device die and the package component through capillary. The method further includes, with the underfill-shaping cover on the package component, curing the underfill. After the curing the underfill, the underfill-shaping cover is removed from the package.

BACKGROUND

Device dies, which include integrated circuit devices such astransistors therein, are often bonded to other package components suchas package substrates, interposers, and Printed Circuit Boards (PCBs).The bonding may be performed through solder bonding, direct metalbonding, or the like. Since the device dies and the respectiveunderlying package components have different Coefficients of ThermalExpansion (CTEs), the bonding structures such as the solder regions andmetal pads often suffer from high stresses. For example, the CTEs ofpackage substrates are often significantly greater than the CTE ofsilicon. As a result, due to the heating and cooling processes in thebonding process, stresses are applied to the bonding structures. Tosolve this problem, underfill is dispensed between the device dies andthe underlying package components to protect the bonding structures.

The dispensing of underfill is through capillary. For example, todispense the underfill into the gap between a device die and a packagesubstrate, the underfill is dispensed onto a surface of the packagesubstrate, wherein the underfill contacts a side of the device die. Theunderfilling process includes a plurality of dispensing steps, with awaiting time following each of the dispensing steps since the capillarytakes time. During the waiting time, the underfill moves into the gapthrough capillary. Each of the dispensing steps and the respectivewaiting time causes the underfill to move further in the gap throughcapillary, until the underfill reaches the opposite end of the gap.

The conventional dispensing method often results in a wide fillet ofunderfill on the side that the underfill is dispensed. On other sides ofthe device dies, the fillet is significantly narrower. This causesnon-uniformity in the profile of the underfill. Since underfill appliesstresses to the device die and the bonding structures between the devicedie and the package substrate, the non-uniformity in the profile of theunderfill causes the stress applied on different parts of the devicedies and the bonding structures to be non-uniform. Furthermore, thefillet width may be different from package to package, and it is hard todetermine and compensate for the stresses. Moreover, the wide fillet ofunderfill may restrict further processes, such as lid attachment orPackage on Package (POP) bonding, which processes occur in the regionsnear the device die.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A, 1B, and 1C illustrate a top view of and cross-sectional viewsof an underfill-dispensing boat in accordance with some embodiments;

FIGS. 2A, 2B, 2C, and 2D illustrate a top view of and cross-sectionalviews of an underfill-shaping cover in accordance with some embodiments;

FIG. 3 illustrates a cross-sectional view showing how theunderfill-dispensing boat and the underfill-shaping cover are alignedthrough guide pins in accordance with some embodiments;

FIGS. 4 through 10 illustrate cross-sectional views of intermediatestages in an underfilling process in accordance with some embodiments;

FIG. 11A illustrates the cross-sectional view of an exemplary packageincluding the dispensed underfill in accordance with some embodiments;and

FIG. 11B illustrates the top view of an exemplary package including thedispensed underfill in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A package and the method of dispensing underfill into the package areprovided in accordance with various exemplary embodiments. Theintermediate stages of dispensing the underfill are illustrated. Thevariations of the embodiments are discussed. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements.

FIG. 1A illustrates a top view of underfill-dispensing boat 20 inaccordance with some embodiments. Underfill-dispensing boat 20 isdesigned to place packages 42 (refer to FIG. 4) thereon. Accordingly,the size and the shape of underfill-dispensing boat 20 are design to fitthe number and the respective sizes of packages 42. For example, FIG. 1Aillustrates that underfill-dispensing boat 20 is designed to fit 3×5packages 42.

In the illustrated embodiments, underfill-dispensing boat 20 includes aplurality of through-openings 22, which are designed to allow theprotrusions 60 of stage 58 to penetrate through, as will be shown inFIGS. 7 and 8. In alternative embodiments, underfill-dispensing boat 20does not include the illustrated through-openings 22.

A plurality of magnets 24 is embedded in underfill-dispensing boat 20.Although FIG. 1A illustrates that there are four magnets 24 disposed tothe four corners of each of through-openings 22, magnets 24 may also bedisposed with other applicable layouts. Since magnets 24 are disposedclose to the bottom side of underfill-dispensing boat 20, as shown inFIG. 1C, magnets 24 are illustrated using dashed lines in FIG. 1A.

Furthermore, a plurality of guide pins 26 is secured on the top surfaceof underfill-dispensing boat 20. Also, although FIG. 1A illustrates thatthere are four guide pins 26 disposed to the four corners of each ofthrough-openings 22, guide pins 26 may also be disposed with otherapplicable layouts.

FIG. 1A also illustrate a plurality of guide pins 27, which are disposedto the corners of underfill-dispensing boat 20. Although FIG. 1Aillustrates that there are four guide pins 27 disposed to the fourcorners of underfill-dispensing boat 20, guide pins 27 may also bedisposed with other applicable layouts, and may have different numbersequal to or greater than three. Guide pins 27 may be formed of a metalsuch as aluminum, copper, stainless steel, for example. In alternativeembodiments, guide pins 27 are formed of organic or inorganic materials,providing guide pins 26 can sustain the temperatures adopted in theheating and curing of the underfill that is to be dispensed.

FIG. 1B illustrates a cross-sectional view of a portion ofunderfill-dispensing boat 20, wherein the cross-sectional view isobtained from the plane containing line 1B-1B in FIG. 1A. FIG. 1Billustrates that underfill-dispensing boat 20 includes base plate 28,wherein through-opening 22 extends from the top surface to the bottomsurface of base plate 28. Base plate 28 may be formed of the materialsincluding, but not limited to, metals (such as aluminum or stainlesssteel), organic materials, glass fiber, ceramic, combinations thereof,and multi-layers thereof.

FIG. 1C illustrates a cross-sectional view of a portion ofunderfill-dispensing boat 20, wherein the cross-sectional view isobtained from the plane containing line 1C-1C in FIG. 1A. FIG. 1Cillustrates that underfill-dispensing boat 20 includes magnets 24embedded into base plate 28 from the bottom side of base plate 28. Inaddition, guide pins 26 are attached to and secured on base plate 28,and protrude above the top surface of base plate 28. Guide pins 26 areused to limit the movement of package component 48 (FIG. 3), and alsohave the function of guiding the placement of package component 48.Guide pins 26 may be formed of a metal such as aluminum, copper,stainless steel, for example. In alternative embodiments, guide pins 26are formed of organic or inorganic materials, providing guide pins 26can sustain the temperatures adopted in the heating and curing of theunderfill that is to be dispensed.

FIG. 2A illustrates a top view of underfill-shaping cover 30 inaccordance with some embodiments. Underfill-shaping cover 30 is designedto shape the underfill during the underfill process. The size and shapeof underfill-shaping cover 30 are also design to fit the number and therespective sizes of package 42, as shown in FIG. 5.

Furthermore, a plurality of openings 37, which are used to alignunderfill-shaping cover 30 to the underlying underfill-dispensing boat20, is formed in underfill-shaping cover 30. In some embodiments,openings 37 are through-openings, and hence are referred to asthrough-openings 37 hereinafter, as shown in FIG. 2C. In alternativeembodiments, openings 37 are not through-openings. Rather, openings 37extend from the bottom surface of underfill-shaping cover 30 up to anintermediate level of underfill-shaping cover 30, as shown in FIG. 2D.Also, although FIG. 2A illustrates that there are four through-openings37 disposed to the four corners of underfill-shaping cover 30,through-openings 37 may also be disposed with other applicable layouts,and may have different numbers equal to or greater than three. Thesizes, shapes, and the positions of through-openings 37 are designed tofit the sizes, shapes, and the positions of guide pins 27 (FIG. 1A), sothat guide pins 27 may be inserted into openings 37 in order to alignunderfill-shaping cover 30 to the underlying underfill-dispensing boat20.

In accordance with the embodiments of the present disclosure, thepositions of through-openings 32 are designed to be aligned to thepositions of through-openings 22 in FIG. 1A when underfill-shaping cover30 is aligned to underfill-dispensing boat 20.

In the illustrative embodiments in FIGS. 1C and 2C, guide pins 27 areattached to underfill-dispensing boat 20, and openings 37 for insertingguide pins 27 therein are formed in underfill-shaping cover 30. Inalternative embodiments (not shown), guide pins 27 are attached tounderfill-shaping cover 30, while openings 37 for inserting guide pins27 therein are formed in underfill-dispensing boat 20. In yetalternative embodiments, underfill-dispensing boat 20 may include bothguide pins and through-openings, and underfill-shaping cover 30 mayinclude both guide pins and through-openings also, wherein the guidepins fit into the respective through-openings.

FIG. 2B illustrates a cross-sectional view of a portion ofunderfill-shaping cover 30, wherein the cross-sectional view is obtainedfrom the plane containing line 2B-2B in FIG. 2A. FIG. 2B illustratesthat underfill-shaping cover 30 includes base plate 38, whereinthrough-opening 32 extends from the top surface to the bottom surface ofbase plate 38. Base plate 38 may be formed of an iron-containingmaterial. Underfill-shaping cover 30 includes slant sidewalls 32A thatare neither parallel to nor perpendicular to the major top surface 30Aand the major bottom surface 30B of underfill-shaping cover 30. Theslant angle α of slant sidewalls 32A may be in the range between about30 degrees and about 60 degrees. It is appreciated, however, that thevalues recited throughout the description are merely examples, and maybe changed to different values.

Non-sticking material 40 is coated on the slant sidewalls 32A ofunderfill-shaping cover 30. Non-sticking material 40 has the propertynot to stick to cured underfill, so that the cured underfill may bereleased from non-sticking material 40. Accordingly, non-stickingmaterial 40 is also referred to as an underfill-releasing coating. Insome embodiments, non-sticking material 40 comprises releasing agents,Polytetrafluoroethylene (PTFE) (known as Teflon, a registered trademarkof Dupont), or other applicable materials. Although not shown, thenon-sticking material 40 may also be coated on the top surface and/orbottom surface of underfill-shaping cover 30. Although FIG. 2Billustrates two sidewalls of opening 32, all four sidewalls of opening32 may have essentially the same profile as illustrated in FIG. 2B, andhave non-sticking material 40 coated thereon.

FIG. 2C illustrates a cross-sectional view of a portion ofunderfill-shaping cover 30, wherein the cross-sectional view is obtainedfrom the plane containing line 2C/2D-2C/2D in FIG. 2A. FIG. 2Cillustrates that underfill-shaping cover 30 includes through-openings37. In alternative embodiments, as shown in FIG. 2D, underfill-shapingcover 30 includes openings 37 that do not penetrate through base plate38.

FIG. 3 illustrates an exemplary embodiment in which guide pins 26 areused to guide package component 48 to the desirable position ofunderfill-dispensing boat 20. Package component 48 is illustrated asbeing disposed between underfill-shaping cover 30 andunderfill-dispensing boat 20 (also refer to FIG. 6). The cross-sectionalview shown in FIG. 3 is obtained from the plane containing line 1C-1C inFIG. 1A. Accordingly, package component 48 is illustrated using dashedlines to indicate that it is not in the illustrated plane. As shown inFIG. 3, during the alignment, guide pins 26 are close to packagecomponent 48, so that package component 48 is aligned to its intendedposition, and is not able to move.

FIGS. 4 through 10 illustrate the cross-sectional views in an exemplaryunderfill-dispensing process in accordance with the embodiments of thepresent disclosure. Referring to FIG. 4, package 42 is placed onunderfill-dispensing boat 20. In the embodiments in whichunderfill-dispensing boat 20 includes through-opening 22, package 42covers through-opening 22. It is appreciated that although FIGS. 4through 10 illustrate one package 42, in the subsequently discussedunderfill-dispensing process, a plurality of packages 42 is placed onunderfill-dispensing boat 20 (FIG. 1A), with each of packages 42 beingaligned to one of through-opening 22 by guide pins 26. The underfillingprocess is also performed on other packages 42.

In some embodiments, package 42 includes device die 44 bonded to theunderlying package component 48 through bonding structures 46. Devicedie 44 may include integrated circuit devices such as transistors,resistors, capacitors, and diodes (not shown). Package component 48 maybe a package substrate, an interposer, a Printed Circuit Board (PCB), apackage, or the like. Package component 48 may also include electricalconnections (not shown, such as redistribution lines and vias)configured to route signals between the features (not shown) on the topsurface and the features on the bottom surface of package component 48.Bonding structures 46 may include solder regions 46A and metalpads/pillars 46B in some exemplary embodiments. In alternativeembodiments, bonding structures 46 may be direct metal-to-metal bondingstructures.

In some embodiments, besides device die 44, there are other componentsbonded or attached to the top surface of package component 48. Forexample, FIG. 4 illustrates stiffener ring 50 attached to packagecomponent 48 through adhesive 52. In addition, passive devices may alsobe bonded to, and electrically coupled to, the top surface of packagecomponent 48. For example, FIG. 4 illustrates passive device 54, whichmay be a resistor, a capacitor, a transmitter, an inductor, or the like.In alternative embodiments, package 42 may not include some or all ofthe illustrated components 50 and 54.

Referring to FIGS. 5 and 6, underfill-shaping cover 30 is placed onpackage 42. Underfill-shaping cover 30 is aligned to the underlyingunderfill-dispensing boat 20 using the alignment mechanism shown in FIG.3. Furthermore, underfill-shaping cover 30 is secured to the underlyingunderfill-dispensing boat 20 through the magnetic force betweenunderfill-shaping cover 30 (which includes a paramagnetic material suchas iron) and the underlying magnets 24 (FIG. 3). The through-opening 32is aligned to device die 44, and device die 44 extends intothrough-opening 32. The underfill-shaping cover 30 may also includeopenings 33 and/or 35, wherein opening 33 forms is designed as anopening ring to fit stiffener ring 50, and opening 35 is designed to fitpassive device 54. Accordingly, after underfill-shaping cover 30 isplaced on package 42, as shown in FIG. 6, stiffener ring 50 is residedin opening 33, and passive device 54 is resided in opening 35. Byforming openings such as 33 and 35, the bottom surface ofunderfill-shaping cover 30 may be placed on the top surface of packagecomponent 48 without being hampered by the components that are attachedor bonded to the top surface of package component 48.

FIG. 7 illustrates some exemplary embodiments in which dispense cover 56is placed on the top surface of underfill-shaping cover 30. In someembodiments, dispense cover 56 has essentially the same top-view shapeas the top-view shape of underfill-shaping cover 30. Dispense cover 56also includes openings that overlap, and having the same top-view shapeand size, as the openings 32 of underfill-shaping cover 30. Furthermore,dispense cover 56 includes slanted surfaces 56A, which are tilted towardopening 32. The surface material of 56 may have a surface tension lowerthan the surface tension of underfill 62 (FIG. 8). For example, thesurface material of 56 is not sticky to underfill 62. In someembodiments, the slant angle β of slanted surface 56A is greater than 0degree and smaller than 90 degrees, and may be in the range betweenabout 20 degrees and about 45 degrees. In alternative embodiments, nodispense cover is placed on underfill-shaping cover 30.

Throughout the description, underfill-dispensing boat 20 andunderfill-shaping cover 30 are in combination referred to as anunderfill-dispensing tool set, which is used for the dispensing ofunderfill. In addition, the underfill-dispensing tool set may furtherinclude dispense cover 56 in some embodiments.

Underfill-dispensing boat 20, the overlying packages 42,underfill-shaping cover 30, and dispense cover 56 are then placed onstage 58, which includes protruding portion 60. Protruding portion 60extends into opening 22 to contact the bottom surface of packagecomponent 48. Stage 58 is configured to secure underfill-dispensing boat20, for example, through vacuum, and is configured to heat package 42.

FIG. 8 illustrates the dispensing of underfill 62, wherein dispensingnozzle 64 is used to dispense underfill 62 on the slanted surface 56A ofdispense cover 56. Since the surface tension of dispense cover 56 issmaller than the surface tension of underfill 62, underfill 62 does notspread on surface 56A. Rather, underfill 62 tends to form a ball shape,and flows into opening 32 (FIG. 7).

FIG. 9 illustrates the underfill 62 after the capillary, which causesunderfill 62 to be filled into the gap between device die 44 and packagecomponent 48. In some embodiments, package 42 is heated by stage 58 tohelp the capillary. The temperature of package 42 may be between about80° C. and about 100° C., for example. The slanted sidewalls ofunderfill-shaping cover 30 confine the profile of underfill 62 to adesirable shape. The amount of underfill 62 is controlled, so thatopening 32 is at least substantially fully filled.

Referring back to FIG. 8, in alternative embodiments in which dispensecover 56 is not used, dispensing nozzle 64 will be aimed at opening 32,so that underfill 62 is dispensed into opening 32 directly.

Next, after the step in FIG. 9 is finished, dispense cover 56 isremoved, and the resulting structure is shown in FIG. 10. Underfill 62is cured, wherein the curing is represented by the curved arrows. Thecuring process may be performed using thermal curing, Infrared (IR)curing, or the like. For example, in a thermal curing process,underfill-dispensing boat 20, packages 42, underfill-shaping cover 30,and underfill 62 are removed from stage 58 (FIG. 9), and are placed inan oven (not shown) to perform the curing process, until underfill 62 issolidified.

After the curing, underfill-dispensing boat 20 and underfill-shapingcover 30 are removed from package 42, and FIG. 11A illustrates theresulting package 42. Since non-sticking material 40 (FIG. 10) is notsticky to underfill 62, underfill-shaping cover 30 can be removed easilywithout damaging underfill-shaping cover 30 and package 42.Underfill-dispensing boat 20 and underfill-shaping cover 30 may then bereused.

As shown in FIG. 11A, underfill 62 includes slanted surfaces 62A,wherein are shaped by the slanted sidewalls of underfill-shaping cover30. The slanted surfaces 62A may extend from the sidewalls of device die44 to the top surface of package component 48.

FIG. 11B illustrates a top view of package 42, wherein thecross-sectional view shown in FIG. 11A is obtained from the planecontaining line 11A-11A in FIG. 11B. It is observed that due to theconfinement of underfill-shaping cover 30, underfill 62 has four sidesextending outwardly from the four sides of device die 44. The four sidesof underfill 62 may have the same profile. For example, the slant angleγ (as shown in FIG. 11A) of all four sides of underfill 62 aresubstantially the same. The heights H1 (FIG. 11A) of four slant surfacesof underfill 62 may also be the same or substantially the same, forexample, with the variations being smaller than about 20 percent,smaller than about 10 percent, or smaller than about 5 percent of heightH1 of either side of underfill 62. The four sides of underfill 62 mayalso spread outwardly for the same distance or substantially the samedistance D1, for example, with the variations being smaller than about20 percent, smaller than about 10 percent, or smaller than about 5percent of distance D1 of either side of underfill 62. Ratio D1/H1 issmaller than 5.0, and may be smaller than about 2:1. As a comparison, inconventional methods for dispensing the underfill, the side from whichthe underfill is dispensed has a D1/H1 ratio greater than 5.0. The othersides, on the other hand, have smaller D1/H1 ratios, for example,smaller than about 2:1.

The embodiments of the present disclosure have some advantageousfeatures. By using underfill-shaping cover 30 to help the underfilldispensing, the profile of all four sides of the underfill is uniform.Furthermore, the width of the underfill can be controlled. Since theprofile and the width of the underfill affect the stress applied onbonding structures (such as 46 in FIG. 11A) and device die 44, thestress is more controllable and predictable, and the reliability of theresulting package is improved.

In accordance with some embodiments of the present disclosure, a methodincludes placing an underfill-shaping cover on a package component of apackage, with a device die of the package extending into an opening ofthe underfill-shaping cover. An underfill is dispensed into the openingof the underfill-shaping cover. The underfill fills a gap between thedevice die and the package component through capillary. The methodfurther includes, with the underfill-shaping cover on the packagecomponent, curing the underfill. After the curing the underfill, theunderfill-shaping cover is removed from the package.

In accordance with alternative embodiments of the present disclosure, apackage includes a package component, a device die over and bonded tothe package component, and an underfill in a gap between the packagecomponent and the device die. The underfill has slanted sidewallsextending from a surface of the package component to a sidewall of thedevice die. The underfill extends beyond four edges of the device die infour lateral directions for substantially a same distance.

In accordance with yet alternative embodiments of the presentdisclosure, an underfill-dispensing tool set is used for dispensing anunderfill. The underfill-dispensing tool set includes anunderfill-dispensing boat and an underfill-shaping cover. Theunderfill-shaping cover includes an opening, and a non-sticking materialon sidewalls of the opening, wherein the non-sticking material is notsticky to the underfill. The underfill-dispensing tool set furtherincludes a plurality of guide pins attached to a first one of theunderfill-dispensing boat and the underfill-shaping cover, and aplurality of openings in a second one of the underfill-dispensing boatand the underfill-shaping cover. The plurality of guide pins isconfigured to be inserted into the plurality of guide pins.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: placing an underfill-shapingcover on a package component of a package, wherein a device die of thepackage extends into an opening of the underfill-shaping cover;dispensing an underfill into the opening of the underfill-shaping cover,wherein the underfill fills a gap between the device die and the packagecomponent through capillary; with the underfill-shaping cover on thepackage component, curing the underfill; and after the curing theunderfill, removing the underfill-shaping cover from the package.
 2. Themethod of claim 1 further comprising: before the placing theunderfill-shaping cover on the package component, placing the packageover an underfill-dispensing boat, wherein during the placing theunderfill-shaping cover on the package component, the underfill-shapingcover is aligned to the underfill-dispensing boat by inserting guidepins of the underfill-dispensing boat into openings in theunderfill-shaping cover.
 3. The method of claim 2, wherein theunderfill-shaping cover is attracted to the underfill-dispensing boatthrough a magnetic force.
 4. The method of claim 1, wherein the openingof the underfill-shaping cover has slanted sidewalls, and wherein afterthe underfill-shaping cover is placed on the package component, lowerportions of the opening have greater widths than upper portions of theopening.
 5. The method of claim 4, wherein the underfill-shaping coverfurther comprises a non-sticking material on the slanted sidewalls, andwherein the underfill is not adhered to the non-sticking material. 6.The method of claim 1 further comprising: after the placing theunderfill-shaping cover on the package component of the package andbefore the dispensing the underfill, placing a dispense cover on theunderfill-shaping cover, wherein the dispense cover comprises a slantedtop surface, with the slanted top surface being slanted toward theopening, and wherein during the dispensing the underfill, the underfillis dispensed onto the slanted top surface of the dispense cover.
 7. Themethod of claim 6, wherein a first surface tension of the dispense coveris lower than a second surface tension of the underfill.
 8. A methodcomprising: placing an underfill-shaping cover over a plurality ofpackage components, wherein a plurality of device dies is bonded to theplurality of package components, and wherein each of the plurality ofdevice dies extends into one of a plurality of openings of theunderfill-shaping cover; dispensing an underfill into the plurality ofopenings of the underfill-shaping cover, wherein the underfill encircleseach of the plurality of device dies through capillary; curing theunderfill; and after the curing the underfill, removing theunderfill-shaping cover from the plurality of package components.
 9. Themethod of claim 8 further comprising placing the plurality of packagecomponents over an underfill-dispensing boat, wherein theunderfill-shaping cover is aligned to the underfill-dispensing boat byinserting guide pins of the underfill-dispensing boat into openings inthe underfill-shaping cover.
 10. The method of claim 8, wherein theplurality of openings of the underfill-shaping cover has slantedsidewalls in the plurality of openings.
 11. The method of claim 10,wherein the underfill-shaping cover further comprises a non-stickingmaterial on the slanted sidewalls.
 12. The method of claim 8 furthercomprising: after the placing the underfill-shaping cover and before thedispensing the underfill, placing a dispense cover over theunderfill-shaping cover, wherein the dispense cover comprises aplurality of slanted top surfaces slanted toward the plurality ofopenings of the underfill-shaping cover, and wherein during thedispensing the underfill, the underfill is dispensed onto the pluralityof slanted top surfaces and flows into the plurality of openings. 13.The method of claim 12 further comprising, before the curing theunderfill, removing the dispense cover away from the underfill-shapingcover.
 14. The method of claim 12, wherein a first surface tension ofthe dispense cover is lower than a second surface tension of theunderfill.
 15. The method of claim 8, wherein the plurality of packagecomponents has a plurality of passive devices bonded thereon, and theunderfill-shaping cover comprises a plurality of additional openings,with each of the plurality of passive devices extending into one of theplurality of additional openings.
 16. The method of claim 8, whereinwhen the underfill is dispensed, the underfill-shaping cover has abottom surface contacting a top surface of each of the plurality ofpackage components.
 17. A method comprising: placing anunderfill-dispensing tool set to contact a top surface of a packagecomponent of a package, wherein a device die of the package extends intoan opening of the underfill-dispensing tool set, with the opening havingslanted surfaces neither parallel to nor perpendicular to a top surfaceof the package component; dispensing an underfill over theunderfill-dispensing tool set, wherein the underfill flows into theopening; with at least a portion of the underfill-dispensing tool set onthe package component, curing the underfill; and after the curing theunderfill, removing the underfill-dispensing tool set from the package.18. The method of claim 17, wherein the underfill-dispensing tool setcomprises an underfill-shaping cover and a dispense cover over theunderfill-shaping cover, and wherein the opening penetrates through theunderfill-shaping cover and the dispense cover, and the method furthercomprises: before the curing, removing a dispense cover from theunderfill-shaping cover.
 19. The method of claim 18, wherein a firstportion of the opening in the underfill-shaping cover has slantedsidewalls, wherein after the underfill-shaping cover is placed on thepackage component, lower portions of the first portion of the openinghas greater widths than upper portions of the first portion of theopening, and wherein a second portion of the opening in the dispensecover has slanted sidewalls tilting toward the opening.